Table 2.
RR of hospitalisation by infection with the SARS-CoV-2 omicron variant compared with the delta variant according to COVID-19 vaccination status among 188 980 cases between Nov 21 and Dec 19, 2021, in Denmark
| Hospitalised (n=2435) | Not hospitalised (n=186 545) | Crude RR (95% CI) | p value | Adjusted RR (95% CI) | p value | ||
|---|---|---|---|---|---|---|---|
| Overall infection with SARS-CoV-2 variant | |||||||
| Delta | 2213/150 311 (1·5%) | 148 098/150 311 (98·5%) | 1 (ref) | <0·0001 | 1 (ref) | <0·0001 | |
| Omicron | 222/38 669 (0·6%) | 38 447/38 669 (99·4%) | 0·39 (0·34–0·45) | .. | 0·64 (0·56–0·75) | .. | |
| By vaccination status | |||||||
| None or only one dose | .. | .. | .. | 0·024 | .. | 0·15 | |
| Delta | 997/69 885 (1·4%) | 68 888/69 885 (98·6%) | 1 (ref) | .. | 1 (ref) | .. | |
| Omicron | 54/7266 (0·7%) | 7212/7266 (99·3%) | 0·52 (0·40–0·68) | .. | 0·57 (0·44–0·75) | .. | |
| Two doses | .. | .. | .. | .. | .. | .. | |
| Delta | 1041/77 441 (1·3%) | 76 400/77 441 (98·7%) | 1 (ref) | .. | 1 (ref) | .. | |
| Omicron | 145/29 992 (0·5%) | 29 777/29 992 (99·5%) | 0·36 (0·30–0·43) | .. | 0·71 (0·60–0·86) | .. | |
| Three doses | |||||||
| Delta | 175/2985 (5·9%) | 2810/2985 (94·1%) | 1 (ref) | .. | 1 (ref) | .. | |
| Omicron | 23/1481 (1·6%) | 1458/1481 (98·4%) | 0·26 (0·17–0·41) | .. | 0·50 (0·32–0·76) | .. | |
Data are n/N (%), unless otherwise indicated. p values in the stratified analysis are tests for interaction terms. Adjusted RRs were adjusted for the basic (a priori) covariates of sex, age (10-year groups), sample period as a continuous variable (week 46+47, 48, 49, or 50), region (capital, central Denmark, north Denmark, Zealand, or southern Denmark), comorbidities in the preceding 5 years (none vs one or more), and previous SARS-CoV-2 infection more than 60 days earlier confirmed by RT-PCR. RR=risk ratio.